Sheet web generation via a tubularly formed web

ABSTRACT

Apparatus for continuously making a tube of melt blown microfibers. A tube so made is useful as a filter element or the like. Melt blown microfibers are deposited from a linear such fiber generating apparatus longitudinally upon a revolvably moving, circumferential surface portion of a mandrel which is supported at one end thereof. A tubular web formed on this belted circumferential mandrel surface is continuously moved towards the open end of the mandrel where it is continuously withdrawn. When being withdrawn, the tube is slit into a sheet, which can be wound on a rotary winder.

United States Patent [191 Bringman SHEET WEB GENERATION VIA A TUBULARLY FORMED WEB [52] US. Cl 425/308; 425/72; 425/324 R;

425/447; 156/426; 264/165 [51] Int. Cl B29d 7/16 [58] Field of Search 150/426, 429, 430, 187,

[56] References Cited UNITED STATES PATENTS 3,157,545 11/1964 Waldron et a1. 156/246 X 3,194,645 7/1965 Green et a1. 425/447 X Kalwaites 156/426 X Gliniecki 425/72 X 51 Sept. 16, 1975 3,736,086 5/1973 Wiltshire et a1. 425/447 X 3,784,667 1/1974 Drostholm et a]. 425/224 X 3,809,514 5/1974 Nunez 425/371 X [5 7] ABSTRACT Apparatus for continuously making a tube of melt blown microfibers. A tube so made is useful as a filter element or the like. Melt blown microfibers are deposited from a linear such fiber generating apparatus longitudinally upon a revolvably moving, circumferential surface portion of a mandrel which is supported at one end thereof. A tubular web formed on this belted circumferential mandrel surface is continuously moved towards the open end of the mandrel where it is continuously withdrawn. When being withdrawn, the tube is slit into a sheet, which can be wound on a rotary winder.

15 Claims, 15 Drawing Figures PATENTEBSEF 1 ems ,995,735

sum 2 o 1 /4 M2 E g- 7 SHEET WEB GENERATION VIA A TUBULARLY FORMED-WEB 7 BACKGROUND OF THEINVENTIO'N In the art of producing a non-woven web of meltblown microfibers, a plurality. of spaced, alignedhot melt strands of polymeric material, or the like, are'extruded downwardly simultaneously directly into the elongated zone of confluence formed by a pair of heated, pressurized, angularly colliding gas usually air) streams, each stream typically being in a flat, sheetlike configuration and being on a different, opposed side of such strand plurality. The gas streams break up the strands into fine, filamentous structures, and move such forwardly in a planar configuration so that a nonwoven web or mat thereof is continuously laid down upon a moving surface. The US. Naval Research Lahoratory, Washington, DC. and Esso Research and Engineering Company, Baytown, Tex. have heretofore reported research and development work on such process. In this process, itis desirable to have the two flattened gas streams employed be as substantially uniform and substantially identical to each other. as practical (as respects such variables as gas composition, gas temper ature, gas pressure, gas volume,,st ream angle with re spect to the forward direction in which the strand plu: rality is being extruded, and the like). Preferably, each gas stream has a temperature about equal to that of the temperature of the strands in one presently preferred mode of practice. I i i In such prior art process, the web thus laid down has usually been continuously deposited upon a moving surface which moves generally. perpendicularly to a planar configuration of the so generated melt-blown microfibers, and the resulting-web has usually been continuously withdrawn fromsuch moving surface in the same general direction of movement. Unfortunately, with this arrangement. only one layer or web of microfibers from each melt blown microfiber generating unit can be utilized to make a product webfAlso, such arrangement does not permit one to make tubular webs. s i

Although it has'heretofore been proposed to generate tubular webs of melt blownlmici'ofibersby lengthwise fiber deposition upon a revolving "mandrel followed by axial movernent of the formed tube from the zone of fiber deposition, such proposal includes no technique for converting the tubular web toa sheet web. If a tubular web so generated cou'ld be for'med into a sheet web, it would be possible to make sheet webs continuously with widths which were independent of the length of the means used to generate a planar configuration of melt blown microfibers which would be highly advantageous. Furthermore, this sheet member would have the advantage of being forrnable of multilayer layers from a single such microfiber generating means. I I

BRIEF SUMMARYOF THE INVENTION There has now been discovered an improved apparatus and process which permits one to generate a web of melt blown microfibers in sheetform using a revolving cylindrical surface. A single melt blown microfiber die assembly can genenrate continuously a web which can have a multiplicity of separately formed layers of such micorfibers, the layers being laid down individually and fused together. The web is laid down in a longitudinal rality of melt blown microfibers in a planar configuration.

Another object is to provide a technique for making melt blown microfibers in sheet form which overcomes the limitations in sheet width heretofore associated with using a given melt blown microfiber generating apparatusof predetermined width. I

Another object is to provide an apparatus wherein a single microfiber die assembly can be used to generate a web in sheet form composed of more than one layer of melt blown microfibers.

Another object is to provide a process for generating a sheet of melt blown microfibers continuously.

Another object is to provide an apparatus wherein means for generating continuously a planar configuration of melt blown microfibers is cooperatively employed with a cylindrical, revolving fiber deposition surface and a slitting apparatus.

Another object is to provide a melt blown microfiber web generating apparatus a continuous belt spirally movable about a supported, generally cylindrically extending surface so that tubular web configurations may be generated thereon and moved therealong axially for slitting into sheet form.

Another object is to provide a process for producing a sheet of non woven fibrous material from a web generating apparatus adapted to produce a web of fibers in a generally planar configuration by going through an intermediate tubular web structure.

Another object isto provide a process of the class indicated wherein the intermediate tube is generated upon acylindrically curved revolvably moving surface and such tube after being formed is advanced axially and slit.

Other and further objects, aims, purposes, advantages, utilities, and features will be apparent to those skilled in the art from a reading of the present specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective diagrammatic view of one embodiment of apparatus of the present invention, some parts thereof broken away and some parts thereof shown in section;

FIG. 2 is a fragmentary view in longitudinal section showing the blade means employed in the embodiment of FIG. 1;

FIG. 3 is a fragmentary view in vertical transverse section further illustrating the blade means of the embodiment of FIG. 1;

FIG. 4 is a view similar to FIG. 2 but showing an alternative embodiment of a blade means suitable for use in the apparatus of FIG. 1;

' FIG. 5 is a view similar to FIG. 3 but further showing the blade means of the embodiment of FIG. 4;

the blade meansof the embodiment of FIG. 8;

FIG. 10 is a partially schematic assembly view in transverse section of the apparatus embodiment of FIG. 1;

FIG. 1 1 is a plan view of one embodiment of a rotating winder assembly adapted for continuously withdrawing a sheet web produced in accord with the practice of the present invention;

FIG. 12 is a vertical sectional view longitudinally taken through the axis of rotation of the rotating winder shown in FIG. 11;

FIG. 13 is a side elevational view of an alternative form of mandrel assembly adapted for use in the present invention;

FIG. 14 is a transverse sectional view taken along the line XIV-XIV of FIG. 13; and

FIG. 15 is a longitudinal sectional view taken along the line XV-XV of FIG. 14.

type of embodiment of the present invention which isherein designated in its entirety by the numeral 15. The apparatus 15 employs a die head or die body 16 in which a thermoplastic resin (not shown) is heated and from which the molten resin is extruded. A preferred resin is a polyolefin, such as a polypropylene. When polypropylene is employed it is heated initially to temperatures in excess of about 600F, and preferably in the range of from about 600 to 800F. The face of die body 16 is equipped with a plurality of spaced, parallel, die openings 17 through which the molten thermoplastic resin is extruded. A hot gas (usually air; not shown) exits under substantially identical pressure and temperature conditions from each elongated slot or orifice l8 and'l9 on either side of the die openings 17. The hot streams of gas function to attenuate the molten extruded resin strands into fibers essentially in a planar configuration which continuously moves away from the die openings 17.

Gas under pressure is conveniently supplied to each of the slots 18 and 19 from respective chambers 21 and 22, which, in the embodiment shown, are located one on either side of the die body 16. Pressurized, heated gas or air is conveniently fed into the chambers 21 and 22, respectively, from conduits 23 and 24.

Although gas temperatures and pressures can vary widely, depending upon such variables as the resin being stranded through die head 16, process conditions, product desired, and many other variables, typical gas temperatures at a slot 18 or 19 range from about 600 to 700F while typical gas pressures at slots 18 and 19 range from about 5 to 30 psig. The width of a gas stream issuing from a slot 18 or 19 typically ranges from about 0.010 to 0.020 inch with the length thereof being dependent upon the length of the die body 16. Gas issuing from a slot 18 or 19 is typically moving at or below sonic of the gas a velocity stream. Preferably,

the interrelationship between each slot 18 or 19 and the die openings 17 is such that the stream angle each of slots 18 and 19 makes with respect to the die openings is identical and ranges from about 15 to 45 with respect to the vertical line midway between the slots 18 and 19 (which preferably is in the center of a plane formed by the microfibers being generated.)

The angularly colliding gas streams strike the plurality of spaced. aligned, hot melt strands issuing from openings 17, slot 18 and 19 being on each side thereof, as indicated hereinabove. Each such strand typically initially ranges in average diameter of from about 0.008 to 0.22 inches, and the spacing between strand centers typically ranges from about 0.030 to 0.050. Preferably, the so-extruded, hot melt strands move downwardly vertically, and the die openings 17 are oriented so as to lie substantially in a (hypothetical) vertical plane lying midway between the two colliding gas streams from slots 18 and 19. In one preferred/mode of operation, the temperature of the gas streams is approximately equal to that of the hot melt. Those skilled in the art will appreciate that in a melt blown microfiber generating apparatus 15 any convenient duct means may be employed to provide the desired air streams on either side of the die openings 17, and that any convenient means of construction may be used for a die body 16 to provide the desired die openings 17, so that a generally planar configuration of melt blown microfibers is adapted to be continuously generated.

Beneath the die body 16 is positioned a revolvably driven mandrel 26. Mandrel 26 is preferably arranged so that the axis 27 thereof is parallel to the (hypothetical) line (not shown) extending through the centers of the die openings 17. Strands from die openings 17, as attenuated into microfibers by gas from slots 18 and 19 and formed into a generally planar configuration are collected or deposited over circumferential surface portions of the mandrel 26 and form thereon a tubular web 28. In the embodiment shown in FIG. 1 the direction of rotation of mandrel 26 is indicated by an arrow.

The mandrel 26 is supported by means permitting such to rotate coaxially on its axis, such a means here being a shaft 29 axially positioned at one end 31 of mandrel 26. The shaft 29 is mounted and journaled for rotational movements relative to a housing 32 by means of a bearing assembly 33. Shaft 29 thus permits mandrel 26 to axially rotate in a cantilever manner. Shaft 29 has mounted thereon a mandrel drive gear 34 which is revolvably driven by a pinion 36. Pinion 36, in turn, is driven by a power head (not shown), such as an electric motor, or the like. The mandrel drive gear 34 in the embodiment shown (see FIG. 10) drives revolvably a sprocket (not shown) which is coaxial with gear 34 and revolvably driven therewith. A roller chain 35 interconnects such sprocket with a timing sprocket 38. Sprocket 38 is keyed axially to a driven shaft 39. The function of shaft 39 is hereinbelow elucidated.

A mandrel 26 can be coated with a slip agent, such as polytetrafluoroethylene or the like, if desired, and a mandrel cylindrical surface can be perforated and subjected to subatmospheric internal applied pressures to help microfiber web formation on such surface during tube formation.

Mounted in the forward end 41 of mandrel 26 is a knife blade 42. Blade 42 is radially upstanding through the circumferential surface of mandrel 26 at end 41 and the edge 43 of blade 42 is substantially parallel to the axis 27 of mandrel 26 with the edge 43 being inclined towards housing 32 so as to face into a tubular web 28 being axially removed from mandrel 26. Blade 42 conveniently stands in a milled plot 44 formed in mandrel 26, and is conveniently held in position by means of a drift pin 46 mounted through a cross drilled channel 47, blade 42 having a hoie therein duly aligned with channel 47. Any convenient blade means may be employed.

One embodiment of means for withdrawing continuously a tubular web of melt blown microfibers from a mandrel 26 over a knife blade 42, thereby slitting the tubular web into a sheet form, is illustrated in FIGS. 1, 11 and 12.. Here, a rotating winder assembly, herein designated in its entirety by the numeral 48, is equipped with a core shaft 48. Core shaft 49 is journaled on a shaft 51 transversely between the leg portions 52 and 53 of a U-shaped frame member 54 for axial rotational movements in bearings (not detailed) one being in such leg portion 52 and 53, respectively. The shaft 51 is driven by a motor 56 by means of a right angle drive provided by a pair of bevel gears 57 and 58, gear 57 being secured to the drive shaft 59 of motor 56 and gear 58 being secured to an end of shaft 51. The motor 56 is driven through appropriate electrical conduits (not shown) through slip rings 61 and 62 mounted on a shaft 64. The shaft 64 is secured to the center of the base 66 of frame 54 by a plate 67, plate 67 being secured to frame 54 by means of bolts 68 which are threadably received in the base 66. The shaft 64 is mounted in bearings 69 and '70 which are adapted to support the frame 54 and the various attachments thereto as herein described, the bearings 69 and 70 being mounted in a frame 71. Frame 71 also mounts the terminal end portion of the driven shaft 39 (mentioned above), shaft 39 being journaled in frame 71 for rotational movements by a bearing 72. Pulleys '73 and 74, on terminal ends of shafts 39 and 64, respectively, are interconnected together by means of a drive belt '76, so that pulley 73 drives pulley 74 which, in turn, rotatably drives the shaft 64, and rotates the core shaft 49 end-overend, the axis 76 of core shaft 49 being normal to the axis 27 of mandrel 26 and also of shaft 64. Thus, core shaft 49 is adapted to revolve end-over-end at a rate approximately the rotational speed of the mandrel 26 and simultaneously to revolve about its own axis 76.

in operation, a web member 77 in sheet form is produced first on the mandrel 26 as tubular web 28. Web 28 is slit by knife blade 42 and the resulting sheet web 77 is convolutely wound about the circumferential surfaces of the core shaft 49 as the shaft 51 thereof is driven by motor 56, the speed of motor 56 being adjusted to provide a predetermined draw rate for remov ing the web 77 from the mandrel 26 axially.

In another form of the present invention, see FIGS. 13 through 15, there is employed a mandrel 81 whose cylindrical hollow body is stationary and which is supported at one end thereof by a frame member 82, a collar 83 on mandrel 81 being employed to aid mounting stability ofthe mandrel 81 in the frame 82. Mandrel 81 may be so supported by any means.

A belt 84 is spirally wound about circumferential surface portions of the mandrel 81 commencing from a slotted aperture 86 located in spaced adjacent relationship to theframe 82 to a slotted aperture 87 located similarly to the slotted aperture 86 on the circumferential surface of mandrel 82 but in longitudinally spaced relationship thereto. Aperture 86 is preferably generally aligned with aperture 87. The belt 84 is arranged so as to have adjacent edge surfaces thereof in the spiral wrap be either in sliding engagement with one another or in close proximate relationship to each other so as to minimize any space gap between adjacent edges of belt 84 about the circumferential surface of mandrel 81. After passing from the exterior circumferential surface of mandrel 81 through slotted aperture 87 into the interior of mandrel 81, the belt 84 is guided by means of rollers, such as rollers 88, 89 and 91 so that its direction of travel is altered, thereby permitting the belt 84 to be returned to a position within the interior of mandrel 81 where it may exit through slotted aperture 86 and again enter the outer circumferential spiral wrap configuration illustrated in FIG. 1, the belt 84 being continuous or endless and formed of a flexible, somewhat resilient material. 1

in the embodiment shown, the roller 88 is revolvably driven by means of an electric motor 92 which is interconnected with the roller 88 by means of reducing gears located within housing 93. Preferably the width of belt 84 is relatively short, being conveniently in the range of from about 0.2 to 0.8 times the outside radius of mandrel 81 although belt widths which are larger or smaller than these relative values may be employed, as those skilled in the art will appreciate. The portion of the circumferential surface of mandrel 81 which is so wrapped with the belt 84 is generally coextensive with that portion of the circumferential surface of mandrel 81 which is equal to the length of the melt blown microfiber generating apparatus 94 (which can be similar to apparatus 15 above), as respects the length of a planar configuration of melt blown microfibers which are to be deposited from a generating apparatus 94 upon the circumferential surface of mandrel 81 in a longitudinal direction, as illustrated, for example, in FIG. 13. The preference in making an embodiment of apparatus of this invention lies in the direction of using few complete turns of a belt 84 about a mandrel 81 because of frictional considerations. Usually from about one to five complete belt 89 turns on a mandrel 81 are most convenient, with two or three turns being presently most preferred. Mandrel diameters ranging from about two to ten inches appear to be convenient mechanically, though larger or smaller diameter mandrels may be employed as those skilled in the art will appreciate.

it is preferred to use a belt 84 on a mandrel 81 without having to employ mechanical anti-friction means, such as roller bearings or the like. While anti-friction means in the nature of coatings on a mandrel 81, such as coatings of a polymeric material like polytetrafluoroethylene or the like, may be employed advantageously if desired in the practice of the present invention, the use of roller bearings can lead to complex, expensive mandrel assemblies, for various obvious reasons. For example, such roller bearings in or on a surface of mandrel 81 would need to be normally aligned, for best utilization, with the direction of spiral movement of belt 84 which is a direction that is slightly different from the axis 96 of mandrel 81. For a preferred contact with a belt 84, transport rollers, such as the rollers 88, 89 and 91, should bisect the angel that the belt 84 makes as it approaches such a roller compared to the angle that such a roller makes with the belt 25 as it departs such a roller following passage thereover,

ing apparatus 94 and impact against the exposed surface portions of the spirally moving belt 84. As microfibe'rs are laid down upon belt 84 in a mat, the motion of} belt 84 imparts a rotational movement thereto so thata product tubular web member 97 moves rotationally during operation of the apparatus of the present invention. A single generating apparatus 94 thus can develop layers of melt blown microfibers in a tubular web member 97 when operating in accordance with the teachings of the present invention. Those skilled in the art will appreciate that the speed at which a belt 84 moves combined with the microfiber deposition rate (the latter including such varibles as fiber type, thickness, etc.) can be used to control weight, density, tubular web thickness and other such web variables in a tubular web member 97 structure made by following the teachings of the present invention. Conveniently and preferably, a generating apparatus 94 generates a planar configuration of melt blown microfibers whose length ranges from about 6 inches to 18 inches, although such ranges which are longer or shorter may be employed conveniently depending upon apparatus and other considerations as those skilled in the art will appreciate.

At the end of the generation of a tubular web member 97 upon a mandrel 81, the interior surface of the tubular web member 97 is readily disengaged from the belt 84 by a stripping action occurring as the belt 84 passes through slotted aperture 87 into the interior of the mandrel 81, the tubular web member 97 continuing to move axially (relative to mandrel 81) and outwardly towards and past the open end 98 of mandrel 81.

Optionally, as those skilled in the art will appreciate, the interior of a mandrel 81 may be vacuumized so as to be maintained at a reduced pressure relative to atmospheric. In this event, the circumferential surface portions of mandrel 81 are conveniently perforated. The belt 84 is porous so as to permit subatmospheric pressures to be exerted on the circumferential outside faces of belt 84, thereby enhancing draw down of melt blown microfibers onto the surface of the belt 84 from the generating apparatus 94. A cooling action is also thus achieved.

A mandrel 81 may be rotatably driven, but such introduces complications in the fabrication of apparatus of this invention.

Belt 84 is driven by roller 88. Thus, roller 88 has a shaft 134 which is supported by a bearing assembly 136 mounted against the inside of mandrel 81. The end of shaft 134 is keyed to a beveled gear 137. Gear 137 engages matingly a beveled gear 138 comprising the internal circumferential surface of a ring gear 139. The circumferentially outer surface 141 of ring gear 139 is geared and engages a drive gear in the nature of pinion 36 in the FIG. 1 embodiment. The desired transport speed for belt 84 is regulated by motor speed and gear sizes, or otherwise as desired. Any convenient means for correlating or synchronizing rotational movement of belt 84 with a blade and with a rotating winder, or the like, may be employed.

Slitting means is provided by a revolvably driven cutter whose edge 99 is in spaced relationship to a beveled edge 101 on the open end 98 of mandrel 81. Cutter 100 is axially revolvably driven on its center shaft 102 through a pair of beveled gears (not shown) by motor 105. These components are suspended by a rim member 103 which circumferentially extends around the open end 98 of mandrel 81, the rim member 103 being supported rotatably (relative to its axis, which is coaxial with axis 96 of mandrel 81) by means of three suspending rollers 104, the rollers 104 riding in a channel 106 on the outside circumferential edge of rim 103. Rim 103 is revolvably driven by a U-belt 107 riding in a mating channel 108 in rim 103. U-belt 107 engages driven sheeve 109 on driven shaft 110. Shaft 110 is driven in a manner similar to shaft 39 described earlier. The driving components are selected so as to cause the cutter 100 to revolve at the same rate of speed as the tubular web member 97. Thus a tubular web member 97 is longitudinally slit by blade 111 as it moves past the end 98 of mandrel 81, as desired in this embodiment.

An alternative form of blade means to that shown in FIGS. 1-3 suitable for use in the apparatus of FIG. 1 is shown in FIGS. 4 and 5. Here a triangular blade 111 with three similar edges 112, 113 and 114 is employed, the blade being positioned similarly to blade 42 in a milled slot 116 in a mandrel 117 and held by a drift pin I 118 positioned in a bore 119 through mandrel 117. Notches 121, 122 and 123 in blade 111 at the lead end of each edge 112, 113 and 114, respectively permit location of blade 111 at a desired angle for each edge 112, 113 and 114 relative to the circumferential face 124 of mandrel 1 17 by a locking pin 126, so that, in operation, a tubular web 126 is brought into contact with an edge, for example edge 112 in FIGS. 4 and 5, of blade 111 at some desired angel thereof. The head of pin 126 is normally maintained in yieldingly biased engagement with a given notch, for example, notch 122 in FIGS. 4 and 5, by means of a spring 127 abutting against the foot of pin 126. Spring 127 and pin 126 ride in a milled slot 128 formed in the rear. face of mandrel 117, these members being held in place in slot 128 by a plate 129 which is bolted over the open side face of slot 12 or by means of bolts 131. To release pin 126 from blade 111, a slot 132 radially extending relative to mandrel 117 is provided in plate 129, and in this slot 132 rides a pin 33 whose base is threadably engaged normally with pin 126, thereby provided manual control of positioning of edges 112, 113 and 114 blade 11 1.

Another alternative form of blade means is shown in FIGS. 6 and 7 for the apparatus of FIG. 1. Here a rotary cutting blade 142 extends through a slot 152 in a mandrel 26" and is mounted for rotational movements on a shaft 143, the shaft 143 being held by bracket 144 and journaled by bearings 146 in bracket 144. Driven gear 147 keyed on shaft 143 interdigitatingly engages the output gear 148 on shaft 149 from reduction gear box 151. Motor is driven by conduits (not shown) engaging slip rings (not shown) on mandrel 26 in a conventional manner.

Yet another alternative form of blade means is shown in FIGS. 8 and 9 for the apparatus of FIG. 1. Here, a rotary cutting blade 153 extends through a slot 154 formed by milling or the like in the circumferential surface of mandrel 26" and is mounted for rotational movements on a shaft 156, the shaft 156 beingheld by a pair of circumferentially spaced legs l59.and 158 radially inwardly extending from a supporting ring 160 and being journaled by bearings(not detailed)'therein. Driven gear 161 keyed onshaft 156 interdigitatingly engages the outputgear l62 on shaft 163 from a reduction gear box 154. Motor 166 is driven by conduits (not shown) engaging slip rings (not shown) on supporting ring 159 in a conventional manner. The supportingiring 159 is itself supported rotatably (relative to its axis, which is coaxial with axis 27 of mandrel 26).=by means of three suspending rollers 167. The rollers 167 being equipped with flanges at their opposite endregions which override the axially spaced outeredges of the circumferentially outer surface of :the supporting ring 159. The supporting ring 159 is revolvably driven at the same rate as the mandrel 26 by means of.a drive pawl which engages the slot 154 thus causingthe supporting ring 159 to rotate withthe mandrel 26. Anyv convenient means may be employed. to drive the supporting ring 159 at the same rpm as the mandrel 26 havingia tubular web 28 thereon during operation of-the apparatus'of FlG.1. a k

As will be appreciated from the description of the foregoing embodiments, sheet webs may be produced by the practice of the=present invention in varying widths from a single melt blown microfiber generating apparatus of fixedleffective length(as respects the width of a planar configuration 'of-fibers generated therewith) by using mandrels of different diameter. Hence, the limitations of the prior'art with respect to width of a web in sheet form produced from'a given microfiber generating apparatus are overcome.

EMBODIMENTS The present invention is further illustra-ted by reference to the following Example. Thoses'ki'lledin-the art will appreciate that other and further embodiments are obvious and within'the spiritand' scope of this invention from the teachingsof this'present Exa mple'taken with the accompanying specification and-drawings."

.EXA P 'E Using an apparatus configuration suchas illustrated in FIGS. 1 through 3 and through 12 a polypropylene web of melt blown microfibers is continuously laid down upon a mandrel to form a tubular web, then slit, and finally convolutely wound into a roll. The mandrel has a diameter of about 30 inches and revolves at a rate of about 12 rpm. The die from which the microfibers are generated has a length of about 40 inches and the die orifices are about 0.015 inches each with the spacing between orifice centers being about 0.050. Strands are extruded from the die at a temperature of about 600F and the air stream on each side of the die head is at about the same temperature at an orifice flow rate of about 400 SCFM and at an angle (relative to the vertical) of about 30. The microfibers at the time they impinge on the cylindrical surface of mandrel are estimated to have average diameters in the range from about 0.002 to 0.010 inches. The tubular web thus formed on the mandrel is continuously longitudinally slit and withdrawn from the mandrel at the rate of' about 100 feet per minute and wound upon a core shaft. Sheet width is about 94.2 inches.

Other and further embodiments and variations of the present invention will become apparent to those skilled in the art from a reading of the present specification taken together withthe drawings and no undue limita tions are to be inferred or implied from the present disclosure.

I claim:

i 1. Apparatusfor continuously making a tube of melt blown microfibers comprising .a. mandrel means,

b. support means supporting said mandrel in the region of one end thereof,

c.-means for continuously generating a generally planar'configuration of melt blown microfibers, said means being adapted to deposit longitudinally upon circumferential surface portions of said man- 3 -drel means a web of melt blown microfibers,

d. means for rotatably moving said -circumferential surface portions as said microfibers are being deposited thereupon and adapted to cause said microfibers to form a tubular web thereupon,

e. means for-axially moving relative to said mandrel means such tubular web comprised of said microfibers towards and past the opposite end region of said-mandrel, and

-fqcutting'means located in said opposite end region and adapted to exert a cutting action on such tubular web as the web moves axially.

*2. The'apparatus of claim 1 further including a. means for continuously collecting generally axially 1 from said opposite end such so slit tubular web; and

b. meansfor rotatably moving said blade means at substantially the same revolution rate as such tubutar web and substantially in the same axes.

3." The apparatusof claim 2 wherein said collecting means revolves at substantially the same rate as such tubular web. t

4. The apparatus of claim 1 wherein said microfiber planar configuration is generally aligned with the axis of said mandrel.

5. The apparatus of claim 2 wherein said collecting means comprises a winder means having a core shaft means rotatably driven on its axis and adapted to wind convolutely upon circumferential surface portions thereof in'a flattened form a tubular web slit longitudinally by'said blade means the axis of said core shaft means being generally normal to the axis of said mandre'l means and in spaced relationship to said opposite end thereof, said core shaft means being further adapted to revolve end-over-end about the axis of said mandrel means at a rate approximating the rotational speed of such tubular web.

6. The apparatus of claim 1 wherein said support means is adapted to permit said mandrel means to revolve and said apparatus includes means for rotatably driving said mandrel means.

7. The apparatus of claim 1 wherein said mandrel means has a chamber defined interiorly thereof and a pair of apertures is formed in circumferential portions of said mandrel means in generally axially spaced relationship to each other and which communicate with said chamber, said apparatus further including a. a continuous flexible belt member, said belt member 1. being spirally wrapped about circumferential portions of said mandrel means between said pair of apertures and adapted to make slidable engagement with said wrapped circumferential portions,

2. extending slidably through each of said apertures at opposite ends of said wrapped circumferential portions,

3. being interconnected with itself through said chamber between said apertures, and

b. belt drive means including guide means within said chamber and adapted to move continuously said belt longitudinally thereof and spirally-about said wrapped circumferential portions in a direction away from said one end.

8. The apparatus of claim 1 wherein said mandrel means has a chambered interior and said circumferential surface portions are equipped with a plurality of aperture means, said apparatus further including means for generating subatmospheric pressures within said chambered interior.

9. The apparatus of claim 5 further including drive means adapted to revolvably drive said spindle endover-end at a rate substantially identical to the rotational speed of said tubular web member on said cylindrical surface.

10. The apparatus of claim I wherein said blade means is mounted in said mandrel means and includes a cutting surface outwardly projecting through such circumferential surface.

11. The apparatus of claim I wherein said blade means is adapted to exert a longitudinal slitting action on such tubular web.

12. The apparatus of claim wherein said cutting surface is a circularly shaped blade member which is revolvably driven about its axis in a direction parallel to the axis of said mandrel means with said blade member axis being located in radially spaced, normal relationship to said mandrel axis.

13. The apparatus of claim 6 wherein said blade means comprises A. rim means circumferentially located adjacent said opposite end region,

B. three shaft means located in circumferentially spaced, fixed relationship around said rim means,

C. wheel means revolvably mounted on each of said shafts and adapted to engage and position circumferentially outer surfaces of said rim means. the wheel means on one of said shafts being drivable,

D. drive means coupled to said one wheel and adapted to rotatably drive said rim means at a rotational speed which is substantially that of said mandrel means, and

E. blade means including blade support means mounted from said rim means and including a cutting surface inwardly projecting through said circumferential surface.

14. The apparatus of claim 13 wherein said cutting surface is circularly shaped and is revolvably driven in a direction parallel to the axes of said mandrel means with the axis thereof being located in radially spaced relationship to said mandrel axis and extending normally thereto.

15. In an improved apparatus for continuously making a web of melt blown microfibers of the type having mandrel means, support means supporting said mandrel in the region of one end thereof, means for continuously generating a generally planar configuration of melt blown microfibers, said means being adapted to deposit longitudinally upon circumferential surface portions of said mandrel means a web of melt blown microfibers, means for rotatably moving said circumferential surface portions as said microfibers are being deposited thereupon and adapted to cause said microfibers to form a tubular web thereupon, means for axially moving relative to said mandrel means such tubular web comprised of said microfibers towards and past the opposite end region of said mandrel, the improvement which comprises in combination a. blade means including support means therefor located in said opposite end region of said mandrel means and adapted to rotatably move about the same axes as said circumferential surface portions at the same rotational speed as such tubular web, and further adapted to exert a slitting action on such tubular web as such so moves axially thereagainst, and

b. winder means having a core shaft rotatably driven on its axisand adapted to wind convolutely upon circumferential surface portions thereof the sheet like web produced from such tubular web by said blade means, the axis of said core shaft being generally normal to the axis of said mandrel means and in spaced relationship to said opposite end thereof, said core shaft being further adapted to revolve end-over-end about the axis of said mandrel means at a rate approximating the rotational speed of such tubular web.

t I i 

1. Apparatus for continuously making a tube of melt blown microfibers comprising a. mandrel means, b. support means supporting said mandrel in the region of one end thereof, c. means for continuously generating a generally planar configuration of melt blown microfibers, said means being adapted to deposit longitudinally upon circumferential surface portions of said mandrel means a web of melt blown microfibers, d. means for rotatably moving said circumferential surface portions as said microfibers are being deposited thereupon and adapted to cause said microfibers to form a tubular web thereupon, e. means for axially moving relative to said mandrel means such tubular web comprised of said microfibers towards and past the opposite end region of said mandrel, and f. cutting means located in said opposite end region and adapted to exert a cutting action on such tubular web as the web moves axially.
 2. extending slidably through each of said apertures at opposite ends of said wrapped circumferential portions,
 2. The apparatus of claim 1 further including a. means for continuously collecting generally axially from said opposite end such so slit tubular web; and b. means for rotatably moving said blade means at substantially the same revolution rate as such tubular web and substantially in the same axes.
 3. The apparatus of claim 2 wherein said collecting means revolves at substantially the same rate as such tubular web.
 3. being interconnected with itself through said chamber between said apertures, and b. belt drive means including guide means within said chamber and adapted to move continuously said belt longitudinally thereof and spirally about said wrapped circumferential portions in a direction away from said one end.
 4. The apparatus of claim 1 wherein said microfiber planar configuration is generally aligned with the axis of said mandrel.
 5. The apparatus of claim 2 wherein said collecting means comprises a winder means having a core shaft means rotatably driven on its axis and adapted to wind convolutely upon circumferential surface portions thereof in a flattened form a tubular web slit longitudinally by said blade means the axis of said core shaft means being generally normal to the axis of said mandrel means and in spaced relationship to said opposite end thereof, said core shaft means being further adapted to revolve end-over-end about the axis of said mandrel means at a rate approximating the rotational speed of such tubular web.
 6. The apparatus of claim 1 wherein said support means is adapted to permit said mandrel means to revolve and said apparatus includes means for rotatably driving said mandrel means.
 7. The apparatus of claim 1 wherein said mandrel means has a chamber defined interiorly thereof and a pair of apertures is formed in circumferential portions of said mandrel means in generally axially spaced relationship to each other and which communicate with said chamber, said apparatus further including a. a continuous flexible belt member, said belt member
 8. The apparatus of claim 1 wherein said mandrel means has a chambered interior and said circumferential surface portions are equipped with a plurality of aperture means, said apparatus further including means for generating subatmospheric pressures within said chambered interior.
 9. The apparatus of claim 5 further iNcluding drive means adapted to revolvably drive said spindle end-over-end at a rate substantially identical to the rotational speed of said tubular web member on said cylindrical surface.
 10. The apparatus of claim 1 wherein said blade means is mounted in said mandrel means and includes a cutting surface outwardly projecting through such circumferential surface.
 11. The apparatus of claim 1 wherein said blade means is adapted to exert a longitudinal slitting action on such tubular web.
 12. The apparatus of claim 10 wherein said cutting surface is a circularly shaped blade member which is revolvably driven about its axis in a direction parallel to the axis of said mandrel means with said blade member axis being located in radially spaced, normal relationship to said mandrel axis.
 13. The apparatus of claim 6 wherein said blade means comprises A. rim means circumferentially located adjacent said opposite end region, B. three shaft means located in circumferentially spaced, fixed relationship around said rim means, C. wheel means revolvably mounted on each of said shafts and adapted to engage and position circumferentially outer surfaces of said rim means, the wheel means on one of said shafts being drivable, D. drive means coupled to said one wheel and adapted to rotatably drive said rim means at a rotational speed which is substantially that of said mandrel means, and E. blade means including blade support means mounted from said rim means and including a cutting surface inwardly projecting through said circumferential surface.
 14. The apparatus of claim 13 wherein said cutting surface is circularly shaped and is revolvably driven in a direction parallel to the axes of said mandrel means with the axis thereof being located in radially spaced relationship to said mandrel axis and extending normally thereto.
 15. In an improved apparatus for continuously making a web of melt blown microfibers of the type having mandrel means, support means supporting said mandrel in the region of one end thereof, means for continuously generating a generally planar configuration of melt blown microfibers, said means being adapted to deposit longitudinally upon circumferential surface portions of said mandrel means a web of melt blown microfibers, means for rotatably moving said circumferential surface portions as said microfibers are being deposited thereupon and adapted to cause said microfibers to form a tubular web thereupon, means for axially moving relative to said mandrel means such tubular web comprised of said microfibers towards and past the opposite end region of said mandrel, the improvement which comprises in combination a. blade means including support means therefor located in said opposite end region of said mandrel means and adapted to rotatably move about the same axes as said circumferential surface portions at the same rotational speed as such tubular web, and further adapted to exert a slitting action on such tubular web as such so moves axially thereagainst, and b. winder means having a core shaft rotatably driven on its axis and adapted to wind convolutely upon circumferential surface portions thereof the sheet like web produced from such tubular web by said blade means, the axis of said core shaft being generally normal to the axis of said mandrel means and in spaced relationship to said opposite end thereof, said core shaft being further adapted to revolve end-over-end about the axis of said mandrel means at a rate approximating the rotational speed of such tubular web. 